[Bug bootstrap/91972] Bootstrap should use -Wmissing-declarations

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91972

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #2)
> (In reply to Alexander Monakov from comment #0)
> > Transition to C++ did not change -Wmissing-prototypes to
> > -Wmissing-declarations, so over time several violations crept in. In
> > particular this penalizes optimization during non-LTO bootstrap (the
> > compiler has to assume the function might be used in another TU, even though
> > in reality all uses are in current file and it simply misses the 'static'
> > keyword).
> 
> Why is it missing the static keyword then? (Or alternatively, why isn't it
> in an anonymous namespace?)
> 
> 
> (In reply to Alexander Monakov from comment #1)
> > Another reason to have -Wmissing-declarations is that otherwise mismatches
> > of unused functions are not caught until it's too late (mismatching
> > definition is assumed to be an overload of the function declared in the
> > header file).
> 
> A more robust way to avoid that problem is to declare the function in a
> namespace, and define it using a qualified name:
> 
> // declaration
> namespace targ
> {
>   void foo(void*);
> }
> 
> // definition
> void targ::foo(class vec_info*);  // ERROR
> 
> Because no foo with that signature was declared in namespace targ it's an
> error, not just a warning.
> 
> Should the coding convention be adjusted to avoid this problem?

Ah, I like the namespace thing for target hooks (possibly langhooks as well).